1. Field of the Invention
The present invention relates to the field of topical application of medicinal or therapeutic material to tissue particularly for the reduction of bleeding, especially for enhancing the formation of clots on the surface of wounds and/or providing specific targeted therapy to a wound site. Devices for applying such medicinal materials are described.
2. Background of the Art
External wounds and concomitant bleeding are the most common injuries suffered by animals. Scratches, cuts, abrasions, lacerations, punctures and other categories of damage to layers of tissue, especially skin, each act to breach the protective tissue and blood vessels, allowing blood to flow out of its normal passageways. Bleeding provides a first line defense against damage from the ancillary effects of the trauma that caused the injury. The flow of blood washes material out of the wound and the blood clots to seal the wound area. The types of materials washed from the wound by the flow of blood from the traumatized area includes material introduced into the wound area by any foreign object which caused the wound (including biological species such as bacteria and viruses and inorganic species such as particulates). The clotting prevents migration of materials into the wound area, and therefore into the animals body, thus reducing the likelihood of subsequent infection of the wound, even after materials originally introduced into the wound have been removed or reduced in volume by the initial blood flow.
Clotting is essential to both the short term and long term process of healing the wound. In the short term, after the wound has been partially cleansed by blood flow, the clotting entraps these removed materials so that they will not easily reenter the wound and stops the blood flow so that excessive blood loss will not occur. In the long term, the clot secures the wound minimizing additional tissue trauma (e.g., from flexing of the area) and preventing additional contaminants from entering the wound and blood stream.
Clotting is a complex biological process, driven by a series of cascading organic/biological chemical reactions which must occur in a specific sequence to cause the final effect of protecting the wound. In lay terms, the events in a simple wound where blood flow has occurred can be described as following a reaction path where                a) Blood cells leak into a wound area;        b) Blood vessels usually contract in the wound area to reduce the flow of blood;        c) Platelets in the blood aggregate and adhere to tissue at the damaged site, even plugging small blood vessels;        d) Platelets also interact with collagen, phospholipids, and tissue factor (a lipid-containing protein or lipoprotein, that stimulates blood clot formation);        e) The platelets break-up and release thromboplastin, a poorly defined mixture of phospholipids and proteins that activate a series or cascade of reactions, usually catalyzed by serine proteases. The final product of these reactions is the enzyme thrombin which catalyses the conversion of the soluble blood protein, fibrinogen, to insoluble fibrin;        f) The platelets provide nuclei upon which fibrin is bound to form the first stage of the moist clot, followed by subsequent maturation of the clot to form a firm coherent mass;        g) Tissue forming cells, fibroblasts, approach the wound and associate with the moist clot to strengthen the region;        h) The clot contracts and dehydrates, usually through evaporative processes, although there may be some absorption of liquid into the tissue;        i) Phagocytes (white blood cells) move into the wound area to ingest microorganisms, cellular debris and any residual foreign matter;        j) Epidermal cells at the edge of the wound divide and build a bridge across the wound.        
The actual chemical and biological processes involved in the clotting process are quite complex and sophisticated. The process must be very selective, forming clots under only exacting conditions, so that clot formation does not occur in the circulatory system where clotting would itself be dangerous, causing phlebitis and certain types of strokes.
Wound management and clotting enhancement for wounds has taken many different paths over the years. There are a wide variety of different methodologies available for the management of wounds, depending, at least in part upon the type of wound and its severity. The two most common and effective treatments for minor bleeding wound management, following cleansing of the wound area, include direct application of pressure to the wound area and the topical application of an absorptive bandage to the wound surface. To assure the reduction of direct or secondary infections, all wound management should include cleansing and application of an antimicrobial agent to the wound area. After this cleansing step, the other methods may follow to control bleeding and prevent contamination of the wound. Direct application of pressure is usually effected by application of pressure manually or with a light wrapping. A sterile article is placed over the wound and pressure applied to the wound through the sterile article (e.g., a fabric, such as gauze, cotton ball, bandage, or other available, preferably sterilized or at least cleaned fabric). The pressure acts to assist in closing blood vessels in the area to reduce blood flow, absorb some of the initial blood flow with the highest content of foreign matter carried therein, and to stabilize the movement of the blood so that clotting is given time to initiate. The application of bandages to the wound area primarily acts to absorb excess blood, flow, provide a longer term barrier over the wound against introduction of foreign agents, protect the clot while it is still fragile (allowing it to dehydrate in the first twenty-four hours), and possibly carry and retain antimicrobial material to the wound surface.
The use of lasers, alone or in combination with topically applied patch materials (e.g., an elastin patch made from animal tissue), has been suggested for field treatment of bleeding wounds, both internal wounds and external or topical wounds. This has been specifically suggested as a field treatment, especially for the military, police, fire, and rescue services. Lasers by themselves can cauterize and seal vessel and organ wounds, and the patch can provide additional structural support for the area. ttp://detnews.com/96/discover/9701/05/12300058.htm.
Many folk remedies have also been applied as abrasion, but not open wound, treatments. For example, www://.drchristopher.com/ail/abrasio3.htm suggests the use of specific natural material treatments for abrasions where the skin has not been broken. The natural herbal agents include wheat grass chlorophyll, comfrey, healing ointment (comfrey, marshmallow, marigold, beeswax and oils), myrrh, plantain (and banana is also well known), and cayenne pepper. These materials may be applied directly to the abrasion area or carried on another surface, often with wetting suggested to retain the herbal abrasion treatment material. An Asian home remedy includes Dit Da Jao (“Iron Wine) which is a tincture remedy applied to relieve pain, stimulate blood flow and chi flow, and break up clots and bruises. The tincture is made up from powdered herbs and alcohol, with strained herbal residue discarded and the liquid tincture applied to the wound surface. The herbs to be used include Arnica blossom, comfrey, blessed thistle, goldenseal root, ginger root, Myrrh, sasparilla root, and witch hazel. Http://ww.aikidofaq.com/n.sub.—section51.html)
Newer technology for wound management is the use of chemical bandages, or literally polymeric film-forming material over the wound area. This technology has passed from a fairly unsophisticated application of liquid glues (e.g., cyanoacrylate adhesives, gelatinous glues, and UV curable polymers) to the wound surface. In 1998, only the second liquid glue was granted FDA approval for use as stitches in addition to clotting enhancement, the glue apparently comprising a formaldehyde content cyanoacrylate. This glue is Closure Medical Corporation's DermaBond™, which is used as an alternative to Baxter HealthCare Corporation's Tisseel™, which is made from two blood proteins that naturally cause blood to clot. The cyanoacrylate must have a strong tendency for tissue irritation and carries a standard recommendation against use with patients with sensitivities to acrylates and formaldehyde, which are fairly common. HealthCare Corporation's Tisseel™, which is made from specific blood proteins thrombin and fibrinogen, is relatively expensive to manufacture. In addition, the use of human or animal derived protein compositions carries the risk of contamination by infectious agents such as hepatitus viruses, Human Immuno-Deficiency (HIV) viruses, or prions such as have been related to mad cow disease (bovine spongiform encephalitis) and Creutzfeld-Jakob disease. The Cryoseal™ clotting system uses cryoprecititated proteins obtained from the patients blood as an adhesive. This fibrin glue adhesive is prepared and applied using a floor-standing, air-driven device in an operating theater.
U.S. Pat. No. 6,060,461 describes a method for enhancing the formation of clots on a wound of an animal where blood is present comprising the steps of applying porous particles with dimensions of from about 0.5 to 1000 micrometers to at least a portion of said wound where blood is present in said wound, allowing said porous particles to remain in contact with said blood in said wound while clotting initiates in said wound. The porous particles may have molecular sieve cutoff values between about 5,000 Daltons and 200,000 Daltons. The pores may comprise from 5 to 75% by volume of the porous particles.
PCT Application Publication WO 00/27327 describes a novel hemostatic composition comprising a substance containing uncharged organic hydroxyl groups and a substance containing at least one of a halogen atom and an epoxy group, which composition induces rapid blood coagulation and hemostasis at a wound or bleeding site. Examples of methods of application of the composition include, but are not limited to bags of materials, patches and bandaid-type patches, segments to be packed into cavities, fibers, fabrics, and the like.
It is known that fibrin clots are formed in vivo based upon the reaction of fibrinogen and thrombin in the presence of calcium ions. The initial phase of wound healing starts after the formation of fibrin clot, and involves the mobilization of cells from surrounding undamaged tissue. Normally, the earliest cells mobilized to the wound are inflammatory where they are active for a period of at least 1-3 days following injury. Subsequently, they are displaced by cells of the mesenchyme lineage which are immobilized into, navigate through and digest fibrin and replace fibrin with extracellular matrix (ECM) of different collagen types, fibronectin and hyaloron. Endothelial cells also infiltrate the fibrin and generate microcapillary structures. Ultimately, these cells replace the provisional fibrin matrix with granulation tissue populated by parenchymal cells and vasculature in secreted ECM.
Human fibroblasts are the major cellular entities responsible for the regeneration of the extracellular matrix (ECM) within the wound bed. Human fibroblasts also express specific membrane receptors to fibrinogen and thrombin. In the case of skin wounds, human fibroblasts reform the matrix of the dermis. For example, during the course of healing of an incisional skin wound, human fibroblasts are mobilized from the surrounding tissue and enter into the fibrin clot, help dissolve it and generate as well as reform the collagens (i.e. type I and type III) in the extracellular matrix. Based upon these properties of human fibroblasts, fibroblast implants have been suggested as a means for supplementing the body's natural wound healing regime (Gorodetsky, R., et al. Radiat. Res. 125:181-186 (1991)).
Benzoylated hyaluronic acid (HA) sheets containing holes or pores have been used as a carrier for fibroblasts and keratinocytes for wound healing (Andreassi, L., et al. Wounds 3(3): 116-126 (1991)). Specifically, HA sheets are cultured with these cells and then affixed to the site of the burn injury, where the cells migrate out of the sheet and accelerate the rate of wound regranulation. A major problem with implanted HA sheets, however, is that they are not metabolized by tissue, are cumbersome to administer, and may result in long-term immunological problems.
Purified fibrin(ogen) (which is known in the art as a mixture of fibrin and fibrinogen) and several of its lytic fragments (i.e. FPA, FPB, D and E) have been shown to be chemotactic to a variety of cells including macrophages, human fibroblasts (HF) and endothelial cells (Gorodetsky, R., et al. J. Lab. Clin. Med., in press (1997); Brown, L. F., et al. Amer. J. Pathol. 142:273-283 (1993); Clark, R. A. F., et al. J. Invest. Dermatol. 79:624-629 (1982); Ciano, P. S., et al. Lab. Invest. 54:62-69 (1986); Dejana, E., et al. J. Clin. Invest. 75:11-18 (1985)). Thrombin also has been shown to exert proliferative effect on various cells including fibroblasts, endothelial cells, and to enhance wound healing in rat skin (Kang, Y. H., et al. J. Histochem. Cytochem. 39:413-423 (1991); Shuman, F., NY Acad. Sci. 408:228-235 (1986); Biedermann, B., et al. J. Lab. Clin. Med. 124:339-347 (1994)).
Fibrin microbeads have been described in the prior art for use as drug delivery systems ((Ho, et al. Drug Dev. and Ind. Pharm. 20(4):535-546 (1994); Senderoff, et al. J. Parenteral Sci. & Tech. 45(1):2-6 (1991)). However, it has not been suggested or taught in the prior art that such fibrin microbeads have chemotactic and/or proliferative effects on any cells. Furthermore, the fibrin microbeads of Ho, et al. and Senderoff, et al. would not be particularly useful or desirable as vehicles for culturing cells. In this regard, the Ho, et al. microbeads contain glutaraldehyde which cross-links proteins and destroys certain biologically active sites, thereby interfering with the binding of the microbeads to cells. Glutaraldehyde treatment may also render the microbeads immunogenic. The Senderoff, et al. microbeads contain essentially the same relatively low degree of cross-linking as fibrin. Thus, the Senderoff, et al. microbeads are not stable in aqueous solutions and therefore would not be useful as vehicles for culturing cells which require matrices that do not readily dissolve in aqueous solutions. U.S. Pat. No. 6,150,505 describes novel fibrin microbeads and their method of manufacture, where the fibrin microbeads are provided in the absence of glutaraldehyde.
One problem in the use of these medical or medicinal treatments is the application of the solids, particulates, fluid or otherwise flowable materials to the desired site. Sprinkling a material over the surface of a wound is effective, but can waste significant amounts of materials. It is desirable to be able to apply the materials more uniformly and specifically to a site. U.S. Pat. No. 6,241,697 shows a non-contact wound covering for covering a wound. A peripheral sealing ring is covered by a barrier layer and this assembly is attached to the skin with an adhesive. The barrier layer and peripheral sealing ring together define a treatment volume over the wound. The barrier layer may include active and passive heaters and the sealing ring may dispense water to control the humidity of the treatment volume. One form of active heat is the transfer of a heated fluid to the wound covering. In effect, an enclosed area is defined around a wound and liquid is directed into the enclosed area through a hose or tube.
U.S. Pat. No. 4,373,519 provides a system for removing liquids from a wound to promote healing, and embeds absorbent materials into a non-woven web that is applied to a surface. The non-woven web may be adhesively secured to the wound area.
These and other descriptions in the art provide means to cover or treat wounds, but improvements in the applying and securing of healing materials to wounds would be useful. It is always desirable to find alternative delivery solutions to wound management problems.